Circuit Description
Important: The following applies to the intake air flow system performance diagnostic that is used in this supercharged engine:
• When referring to the "intake manifold models", the plenum volume between the throttle body (TB) and the supercharger is considered to be the intake manifold. • When referring to "engine pumping", the supercharger and the intercooler plenum are considered to be part of the engine. • The manifold absolute pressure (MAP) sensor that resides in the engine intake manifold is used to adjust the engine air flow estimates to balance the air flow models.
The supercharger inlet absolute pressure (SCIAP) sensor measures the absolute pressure of the air just after the TB, thus just before the supercharger. The plenum volume between the TB and the supercharger is where this sensor is located, and for the purpose of this diagnostic, this area is considered to be the intake manifold. The diaphragm within the SCIAP sensor functions in the same manner as the barometric pressure (BARO) sensor. These sensors are not interchangeable.
The intake air flow system performance diagnostic provides the within-range rationality test for the mass air flow (MAF), the SCIAP, and the throttle position (TP) sensors. This is an explicit model-based diagnostic containing four separate models for the intake system.
| • | The throttle model describes the flow through the throttle body and is used to estimate the MAF through the throttle body as a function of BARO, throttle position, intake air temperature (IAT), and estimated SCIAP. |
| • | The first intake manifold model describes the intake manifold and is used to estimate SCIAP as a function of the MAF into the intake manifold from the throttle body and the MAF out of the intake manifold caused by engine pumping. The flow into the intake manifold from the throttle uses the MAF estimate calculated from the throttle model. |
| • | The second intake manifold model is identical to the first intake manifold model except that the MAF sensor measurement is used instead of the throttle model estimate for the throttle air input. |
| • | A fourth model is created from the combination and additional calculations of the throttle model and the first intake manifold model. |
The estimates of the MAF, the SCIAP, and the TP that are obtained from this system of models and calculations are then compared to the actual measured values from the MAF, the SCIAP, and the TP sensors and to each other to determine the appropriate DTC to fail. The following table illustrates the possible failure combinations and the resulting DTC or DTCs.
Throttle Model | First Intake Manifold Model | Second Intake Manifold Model | Fourth Model | DTCs Passed | DTCs Failed |
|---|---|---|---|---|---|
X | X | Pass | Pass | P0101 P0121 P012B P1101 | None |
Pass | Pass | Failed | Pass | P0101 P0121 P012B P012B P1101 | None |
Failed | Pass | Failed | Pass | P0121 P012B P1101 | P0101 |
Pass | Failed | Failed | Pass | P0101 P0121 P1101 | P012B |
Failed | Failed | Failed | Pass | P0121 P1101 | P0101 P012B |
X | X | Pass | Failed | P0101 P012B P1101 | P0121 |
Pass | Pass | Failed | Failed | P0101 P0121 P012B P1101 | None |
Failed | Pass | Failed | Failed | P0101 P0121 P012B | P1101 |
X | Failed | Failed | Failed | P0101 P0121 P012B | P1101 |
If the engine control module (ECM) detects that the actual measured air pressure from the SCIAP sensor is not within range of the calculated air pressure for the SCIAP sensor that is derived from the system of models, DTC P012B sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P012B Supercharger Inlet Absolute Pressure (SCIAP) Sensor Performance
Conditions for Running the DTC
| • | DTCs P0120, P0121, P0220, P0506, P0507, P012C, P012D, P2135 are not set. |
| • | The engine speed is between 400-6,400 RPM. |
| • | The engine coolant temperature (ECT) is between 70-125°C (158-257°F). |
| • | The IAT is between -7 to +125°C (+19 to +257°F). |
| • | The change in the TP is less than 5 percent. |
| • | The above enabling criteria must be stable for more than 5 seconds. |
| • | DTC P012B runs continuously when the above conditions are met. |
Conditions for Setting the DTC
The ECM detects that the actual measured air pressure from the SCIAP sensor is not within range of the calculated air pressure for the SCIAP sensor that is derived from the system of models by more than 20 kPa for more than 0.5 second.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Step | Action | Values | Yes | No | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||||||||
2 | Observe the DTC information with a scan tool Are DTCs P0641, P2228, P2229 set? | -- | Go to DTC P0641 or P0651 , and DTC P2228 or P2229 | Go to Step 3 | ||||||||||||||
3 |
Important: The harness connectors for the following sensors are of the same configuration but are not interchangeable.
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 4 | ||||||||||||||
4 | Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 5 | ||||||||||||||
5 | Inspect the throttle body and the throttle valve for the following conditions:
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 6 | ||||||||||||||
6 | Test for an intermittent and for a poor connection at the SCIAP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 7 | ||||||||||||||
7 |
Is the SC Inlet Pressure Sensor parameter less than the specified value? | 0.1 V | Go to Step 8 | Go to Step 11 | ||||||||||||||
8 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 10 | Go to Step 9 | ||||||||||||||
9 | Is the voltage more than the specified value? | 5.2 V | Go to Step 12 | Go to Step 13 | ||||||||||||||
10 |
Important: All electrical components and accessories must be turned OFF.
Is the resistance more than the specified value? | 5 ohms | Go to Step 14 | Go to Step 16 | ||||||||||||||
11 | Test the SCIAP sensor signal circuit between the engine control module (ECM) and the SCIAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 15 | ||||||||||||||
12 | Test all branches of the 5-volt reference circuit that is shared with the SCIAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 15 | ||||||||||||||
13 | Test the 5-volt reference circuit between the ECM and the SCIAP sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 15 | ||||||||||||||
14 | Test the low reference circuit between the ECM and the SCIAP sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 15 | ||||||||||||||
15 | Test for shorted terminals and for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17 | ||||||||||||||
16 | Replace the SCIAP sensor. Refer to Supercharger Air Inlet Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- | ||||||||||||||
17 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 18 | -- | ||||||||||||||
18 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 19 | ||||||||||||||
19 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||||
